The genetic control of the synthesis and function of macromolecular cell structures is studied by two approaches: 1. Mutations in structural and regulatory genes controlling chlorophyll synthesis in barley are used to analyze the role of the membrane protein protochlorophyll holochrome in the regulation of porphyrin synthesis and in the assembly of the photosynthetic membrane. Studies on organelle biogenesis with the aid of gene mutants concern the synthesis and function of membrane and soluble proteins of chloroplasts. 2. Precise pairing of homologous chromosomes in meiosis is a prerequisite for crossing over, and is accomplished by the ribonucleoproteins of the synaptinemal complex. The assembly of the synaptinemal complex and its function in chromosome recognition is studied in certain Drosophila, Bombyx and maize genotypes as well as in Lilium, Neottiella and man. Isolation and chemical characterization of proteins specific for meiosis in yeast are attempted. Such isolation is a prerequisite for studying the questions, whether certain components of the synaptinemal complex are products of specific recognition genes and others serve functions in the molecular events of crossing over. BIBLIOGRAPHIC REFERENCES: Stern, H., Westergaard, M. and von Wettstein, D., 1975: Presynaptic events in meiocytes of LILIUM LONGIFLORUM and their relation to crossing-over: a pre-selection hypothesis. Proc. Nat. Acad. Sci. USA 72, 961-965. Wettstein-Knowles, P. von, 1976: Biosynthetic relationships between beta-diketones and esterified alkan-2-ols deduced from epicuticular wax of barley mutants. Molec. Gen. Genet. 144, 43-48.